1. Field of the Invention
The present invention relates to a real-image variable magnification view finder having an objective optical system of positive power, a condenser lens located in the vicinity of the image forming plane of the objective optical system, an eyepiece optical system of positive power, and an image erection optical system.
2. Description of the Related Art
In a conventional real-image variable magnification (power) finder for a compact camera, the zoom ratio (magnification) is usually less than 3. A known view finder having a zoom ratio- greater than 3 is large or expensive, contrary to realization of a small and less expensive compact camera.
For example, in a real image variable magnification finder disclosed in Japanese Unexamined Patent Publication No. 6-102453, an objective optical system is composed of a positive first lens group, a negative second lens group, a positive third lens group, and a fourth lens group having at least one negative lens element, in this order from the object side. However, in this view finder, the zoom ratio is approximately 2 which is low, and a large number of the lens elements are necessary.
In a real image variable magnification finder disclosed in Japanese Unexamined Patent Publication No. 2-173713, an objective optical system is composed of a positive first lens group, a negative second lens group, a positive third lens group, and a low powered fourth lens group. In this view finder, the zoom ratio is approximately in the range of 2.5 to 3.5, which is relatively high, but the view finder is large and a large number of expensive lens elements having a high refractive index are necessary.
In a real-image variable magnification finder disclosed in Japanese Unexamined Patent Publication No. 8-43885, an objective optical system is composed of three lens groups consisting of a positive first lens group, a negative second lens group, and a positive third lens group, in this order from the object side. In this view finder, the zoom ratio is higher than 3 and less number of lens elements are needed. However, the view finder is relatively large.